Damage to ligaments, such as anterior cruciate ligaments (ACL) and the posterior cruciate ligaments (PCL), cartilage, and tendons has become a relatively common occurrence and often requires surgical repair. Often, the ACL or the PCL is ruptured or torn as a result of physical activity and, consequently, various surgical procedures have been developed for replacing or reconstructing these ligaments.
The knee joint is often repaired by substituting a harvested or synthetic replacement ligament for the damaged one. Commonly, a substitute ligament or graft is inserted into tunnels reamed in the femur and tibia bones. Once anchored in place, the graft ligament is able to cooperate with the surrounding bone and tissues and thereby perform the functions of the damaged ACL or PCL. One problem associated with this technique is locating the proper position and angle for drilling the tunnel in the femur (femoral tunnel). Several methods have been developed for determining the location for drilling the femoral tunnel.
One such method is to insert a drill guide and guide pin through the incision and tunnel in the tibia and into the femur. In order to accurately shoot a guide pin for femoral tunnel preparation, most surgeons use an “over the top” drill guide, as shown in U.S. Pat. No. 5,320,115 to Kenna and U.S. Pat. No. 5,320,626 to Schmieding. This type of drill guide references the back wall of the femoral notch to deliver the guide pin a certain distance in millimeters from the back wall. The distance desired is chosen by the surgeon depending on the diameter of the ACL graft to be used. A reamer will be used over the guide pin to create the femoral tunnel, and 2 mm of back wall or less should be present behind the tunnel. It is undesirable to ream through the back wall and in many cases the chosen fixation method will not work if this occurs. For example, if an 8 mm ACL graft is to be used then a 6 mm over the top guide is selected. This will place the guide pin 6 mm from the back wall. When an 8 mm reamer is used over the guide pin, then 2 mm of back wall will remain.
Traditionally the over the top guide is placed through the drilled tibial tunnel to position the guide easily on the back wall. When the tibial tunnel is drilled properly, however, the over the top guide is fairly vertical in the notch in the frontal plane because the placement of the guide is dictated by the angle of the tibial tunnel. Recent studies are indicating that a more lateral femoral tunnel placement is desirable. Yet, this angle is difficult to reach when using a traditional over the top guide in the tibial tunnel, so some surgeons are recommending using a second low medial portal to place the over the top guide. This allows for more lateral positioning in the AP plane, but, consequently, starting more superior decreases the angle of pin placement in the lateral plane, increasing the chance of reaming through the back wall of the femur.
While the medial portal can be used, and has the advantage of allowing for a more lateral femoral tunnel, it has several disadvantages that make it undesirable. Notably, using the medial portal involves making a second incision in the tissue, which results in unnecessary fluid loss and an additional scar. Furthermore, in order to use the medial portal, hyperflexion of the knee must be performed which is sometimes difficult to do. Also, while some have probably begun designing new instruments and techniques for those who are comfortable using the medial portal, most surgeons are most familiar and most comfortable with using the tibial tunnel as a reference for placing the femoral tunnel. These surgeons are not likely to drastically change the technique they are comfortable with. Last, as stated above, using the medial portal increases the chance of reaming through the back wall of the femur which can make it difficult or impossible to properly secure the graft ligament. Using the tibial tunnel as a reference puts the guide pin in a safe trajectory so that the back wall will not be violated during reaming.
It is therefore desirable to have a surgical drill which uses the tibial tunnel as a reference for placing the femoral tunnel. In addition, it is desirable to have a drill guide which allows for more lateral femoral tunnel placement.